v0.2.34

• Implement support for TTML (Timed Text Markup Language) subtitles that are encoded using the STPP codec and packed in fragmented MP4 segments. These subtitles are provided as a separate media stream of fMP4 segments, that the media player retrieves incrementally. This library is able to extract the XML-formatted TTML fragments from an MP4 fragment, to parse the TTML fragment to extract <style>, <region> and <p> elements, and to serialize them to a single merged TTML subtitle file. We only support the text-only IMSC1 profile for subtitles ("stpp.ttml.im1t"); the image-only profile ("stpp.ttml.im1i") is not supported.

• Implement support for VTT subtitles that are distributed in fragmented MP4 segments, using SegmentTemplate or SegmentTemplate>SegmentTimeline addressing. This is a complement to the existing support for VTT subtitles distributed as a sidecar.

• Subtitles embedded in an output MP4 file now include the subtitle language in the metadata for the subtitle track.

• Account for @endNumber in a SegmentTemplate element. This attribute does not seem to be officially documented in the ISO and DASH-IF specifications, but support for it is implemented in the reference dash.js player, and the attribute is used by some manifests in the wild.

• When retrieving content from a multi-codec manifest (that includes multiple Representation elements with different video codecs), it is now possible to specify a preference ordering for the video codec. Use the new commandline option --prefer-video-codecs.

• When retrieving content from a manifest that offers multiple Representation elements for the video stream (with different resolutions, or different codecs for example), it is now possible to select the Representation to retrieve by its id attribute. You can specify the full
  id of the desired Representation, or a substring of the id which will then be combined with other user-specified preferences (on video width, height, codec and quality) to select the video stream that will be retrieved. Use the new commandline option --want-video-id.

• Improve the way in which video stream selection is implemented, to allow selection based on both video width/height and codec and quality, in situations where multiple Representations are available with the same resolution but different codecs or quality settings. If there are multiple Representations with the same “score” with respect to a user-specified parameter (for example, several Representations with the same video resolution but with different codecs), all identical score Representations will now be passed on to the next filtering stage, whereas previously only one Representation (the first listed in the manifest) would be selected. Filtering of video Representations takes place in the following order:

  • id attribute substring
  • video width
  • video height
  • video codec
  • quality/bandwidth (defaulting to the lowest quality and file size)